The present invention relates to an image sensor, and more particularly, to a backside illuminated image sensor.
In a complementary metal oxide semiconductor (CMOS) image sensor, a light receiving element, a digital control block, and a peripheral circuit such as an analog-to-digital converter are arranged at a finite area within a chip. Thus, an area ratio of a pixel array per a chip area is limited to about 40%. Furthermore, a pixel size is greatly reduced for implementation of high quality images. Accordingly, an amount of light that one light receiving element can collect is reduced and noise is increased, causing various problems such as image loss.